New naphtho[2,1- <i>b</i> ]furan-2,5-dione and isocoumarin derivatives from bambusicolous fungus <i>Gelatinomyces siamensis</i>

Two new compounds, 6-hydroxy-1-(4-hydroxyphenyl)naphtho[2,1-<i>b</i>]furan-2,5-dion (<b>1</b>) and 3-methyl-6-<i>α</i>-L-rhamnopyranosyl-2<i>H</i>-chromen-2-one (<b>2</b>), along with three known compounds (<b>3</b>-<b>5</b>) were isolated from the rare bambusicolous fungus <i>Gelatinomyces siamensis</i>. The structures were elucidated through the analysis of IR, NMR and HRESIMS spectrographic data. Compound <b>1</b> exhibited cytotoxicity against HeLa, HT29, MCF-7 and PC-3 cells, but was not toxic against normal Vero cells. The most abundant metabolite, oosporein (<b>5</b>), exhibited significant cytotoxic effects against all tested cancer cells.